Technical Field
The present invention relates to powder overlay nozzles, and particularly to a powder overlay nozzle used for laser cladding processing for forming an overlay layer (cladding layer) on a workpiece.
Background Art
Conventionally, laser processing is known Whereby; in order to increase the durability of a valve seat of an engine cylinder head while increasing its design freedom, the valve seat is irradiated with laser beam while a powder (powdered) overlay material is supplied to the valve seat, forming an overlay layer (cladding layer) while the valve seat and the laser beam are relatively rotated. Specifically, the cylinder head that has been subjected to a machining process required for the engine combustion chamber, such as a valve opening forming process, is irradiated with laser beam while an area of the cylinder head that is to be formed into the valve seat is supplied with the powdered overlay material. The powdered overlay material may include a copper alloy and the like having abrasion resistance. In this way, a ring-shaped overlay layer, namely an overlay bead portion, that is to eventually provide the valve seat, is formed. Generally, the technology is referred to as laser cladding processing.
In the above laser cladding processing, generally a coaxial nozzle (powder overlay nozzle) of double-pipe structure is adopted which is configured to pass laser beam while discharging the powder metal from around the laser beam. As an example of such conventional powder overlay nozzle, a powder metal overlay nozzle illustrated in FIG. 13 is known (Patent Literature 1).
The conventional powder metal overlay nozzle illustrated in FIG. 13 includes a columnar body portion A and a nozzle portion B coaxially joined to the body portion A. The body portion A includes an outer member C and an inner member D fitted in a central space of the outer member C. Between the outer member C and the inner member D, there are formed a ring-shaped gas charged space F charged with inert gas, and a powder metal charged space F charged with powder metal as well as carrier gas. Into the powder metal charged space F, a plurality of supply channels G are opened. The powder metal charged space F is divided by dividing, portions I into charged regions corresponding to the respective supply channels G. At the bottom of the powder metal charged space F, there are formed a number of guide holes J for guiding the powder metal to the nozzle portion B, the guide holes J being disposed along the circumference of the bottom in parallel with an axis L and opening on the lower surface of the outer member C.
The powder metal overlay nozzle is linked with a laser beam generation device for a laser processing head, with the powder metal supply channels G of the body portion A being connected to a powder metal supply source (Which may also be referred to as a “feeder”) via a supply pipe. The powder metal overlay nozzle is configured such that laser beam R emitted from the laser beam generation device connected over the body portion A passes through a laser passage K inside the body portion A and the nozzle portion B and irradiates a processing portion W of a workpiece via an irradiation opening M. On the other hand, the powder metal P supplied from the feeder to the powder metal supply channels G via the supply pipe together with the carrier gas is charged equally into the respective charged regions partitioned by the dividing portions I of the powder metal charged space F. The charged powder metal P passes through the guide holes J and discharge passages N and is discharged out of a discharge opening Q to an area around the processing portion W. The discharged powder metal P is melted by the laser beam R, whereby an overlay layer is formed on the processing portion W.